Ibanez DE-7 mods thread

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Re: Ibanez DE-7 mods thread

Postby kroaton » 04 Oct 2014, 22:29

That sounds awesome.

Can't wait to give it a whirl.
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Re: Ibanez DE-7 mods thread

Postby loylo » 07 Oct 2014, 15:23

Thanks kroaton! :D

I managed to gather my simulations. So I'll try to explain what I've done.
I must precise that my version of DE7 is the chinese one, corresponding to this scheme:
http://www.ibanez.com/parts/2004_PARTS/ ... DE7-02.pdf

The chinese version is different from the taïwanese version almost only on the echo chip side. The input/output, the compander and the feedback lopp/repeats signal paths seem identical. The distortion/filter circuit of the Echo mode is identical, except it is fed with a +5V power in the taïwanese version, insted of a +9V power in the chinese one.

I'll keep the schematic of DWBH (from the taïwanese version) as a reference:
Image

Tone control

The AC analysis of the original distortion/filter circuit shows that the signal at the output is at +6dB approximatively, within a band of 70 Hz to 1.3 kHz (which are frequencies at -3dB relatively to the max gain. I used this criteria for reference, those may not precisely be cutoff freq).
Original filter AC analysis.JPG


I first tried the mod described by DWBH in the first page, that is a 20k log pot for R31.
Here is the AC analysis, with the tone pot increasing from 0 (green) to 20k (purple) by 25% increments.
R31 tone mod AC analysis.JPG


The -3dB (relatively to the max gain of each curve) upper frequency varies from 500 Hz (in purple) to 2 kHz (in green), so this mod really works as a high cut control for the repeats.
The problem is (as I said earlier and as you can see it from the graphs) that the gain of the signal is also reduced as the high cut control is raised (from 7.5dB for the green curve to -4dB for the purple curve). As the total gain is reduced in the feedback loop, the number of repeats is decreased, which is a major drawback for me. I want a tone control which keeps the number of repeats constant (set by the feedback knob).

That is why I tinkered with this mod and I suggest to replace:
C33: 6n8 -> 3n3
C32: 68n -> 10n
R29: 10k -> 10k lin pot with pins 1 and 3 between pin 6 and 7 of IC8B, + 56n (or 47n) cap across the wiper and pin 7 of IC8B.
New tone filter mod.JPG


Here is the AC analysis of the signal at the output iof the circuit. The filter pot is increased from 0=no filtering (green curve) to max= more hi cut (purple curve).
New tone filter AC analysis.JPG


As it can be seen, the gain remains more constant (from 6.7 dB when no filtering to 5 dB when max filtering). And the hi cut range goes from 4 kHz (-3dB freq relatively to the max, green curve) to 400 Hz (-3dB freq relatively to the max, purple curve).

If, like me, you don't have a 10k lin pot, but for example a 50k lin pot, you could use it. But you have to R30 with a value approximatively the same (a bit less) as your pot (like a 47K resistance for a 50k pot) in order to keep IC8B at unity gain. You may also have to decrease the cap across the pot to something like 10n.



Saturation control

I also added a saturation control along with my new tone control, in order to simulate the saturation of the magnetic heads of a tape echo in bad condition.

The original saturation/filter circuit clips the signal a little bit. A 500 Hz sine wave (in blue) is clipped as shown by the green curve at the output of the circuit.
Original filter clipping.JPG


As this circuit is similar to a Tubescreamer, a way to increase the clipping consists in inscreasing the gain of IC8A which contains the diodes clipping in its feedback loop, by increasing R27.
But as the total gain of the circuit is increased, il will also increase the number of repeats, just as described in the tone mod.
In order to keep the gain constant, I moved the diodes clipping a the output of IC8A, just like the clipper configuration of the MXR Distortion + / Boss DS1 / Fulltone OCD.
In order to make the signal bigger than the forward voltage of the diodes, it needs to increase the gain of IC8A, by increasing R27 (it also needs to decrease C33 to keep the same amount of filtering), and decrease the gain of IC8B (by increasing R30) in order to keep the total gain of the circuit around 6 dB.

So here are the values I recommand:
R27: 4k7 -> 22K
C33: 6n8 (or 3n3 if you have already made the tone mod) -> 1n
R30: 8k2 -> 47k
D6 and D7: move them outside the feedback loop of IC8A; at the junction of R31 and R30, with the other end connected at vref through a log pot (20k works well) which becomes the "saturation control".

Saturation mod.JPG


With the configuration above, the gain remains constant around 6.7dB wherever the saturation pot is set. And the tone control also keeps acting the same as described above, wherever the saturation pot is set.

This new saturation/filter circuit can go from no clipping (green curve) to max clipping (pruple curve), with a 500mV peak to peak, 500 Hz sine wave at the input:
New filter clipping control.JPG



Sorry for this long and semi-technical boring post. I can sum up the mods if it's needed and if the other informations are boring. :oops:

I'd like to record soundclips of my DE7 to let you ear these mods. Maybe in the future...

And I think I've managed to work out a trails mod. But I'd like to test it on my DE7 before disclosing it. Wait and see. :P
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Re: Ibanez DE-7 mods thread

Postby kroaton » 08 Oct 2014, 22:48

:applause:

This thread is probably going to end up being the definitive DE7 mod thread on the web and mostly so due to your incredible contribution.

Phenomenal job mate, I can't wait to try all of this out once I get back home.

Thanks again for taking the time to break it all down and post the LTspice sims, it's finally gotten me motivated to start messing around with Spice.
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Re: Ibanez DE-7 mods thread

Postby loylo » 16 Oct 2014, 16:13

Thanks! :D
Glad to share this if it may be of any help.

And here is what I propose for the trails mod:
As it has been said earlier in this thread, bypassing Q6 (by shunting the drain and source pins or by lifting D5) is not enough: it allows only 1 repeat to be trailed after pedal is bypassed. It acts like this because Q4 is blocking the signal back to the delay IC in bypass mode.

So Q4 (at the output of the SA571 compander) also have to be bypassed, by shunting the drain and source pins or by lifting D4. But by doing so, the dry signal is still sent to compander and then to the delay IC, and the effect is always on, whether you activate the stompswitch or not! So the dry signal has to be cut right after the junction of R6 and R7 and before the junction circled in red in the schematic below (where the feedback signal joins in).
Original bypass operation.JPG


Then, a FET configured as a switch (just like Q4 and Q6, with 100k between the source and the 4.5V reference and a 1N4148 diode between the gate and the flip-flop circuit) has to be added, between point A and B in the schematic below.
Trails bypass mod.JPG

Finaly, you can bypass Q4 and Q6, for example with a DPDT shunting the drain and source of both FETs.

I found out a little drawback: in trails mode, with the DPDT shunting Q4 and Q6, and the FET switch added to cut the dry signal, there is a little bit of latency when I switch from effect-off to effect-on before the signal is actually delayed. But it is not so annoying. I added a SPDT to shunt the FET when I set the DPDT in normal bypass; but I may have to tinker the FET switch to eliminate this drawback.

Here are some pics of my DE7:
First the PCB with the led and orginal Echo/Delay and Range switchs. This is where I added the Tone and Clipping controls of the Echo mode, with the 2 sliders I salvaged from a broken autoradio.
P1050123_2.JPG


I choose those sliders instead of ordinary pots because of its low profil, which goes well along the tone lock controls of the pedal, as you can see on this pic:
P1050131_2.JPG

You can also see the metal jack socket, which is a stereo jack for the effect loop send and return.

And I choose to hide inside the battery compartment the DPDT for the trails mode and the SPDT shunting the FET on the dry signal. No need to drill the enclosure as I don't have to often swith between trails and normal bypass.
P1050128_2.JPG



kroaton wrote:This thread is probably going to end up being the definitive DE7 mod thread on the web

I still have a lot of mods in my mind in order to turn this thread into the "definitive DE7 mod thread"! :P
But I don't know if all of these mods are feasible, and if I'll be able to find out how to do them.

For example:
- add a "wow and flutter" control on the Echo mode, in order to simulate even more a tape echo.
- add a tap tempo
- add an Atmega or another microcontroller in order to change from delay mode to echo mode and vice versa with 2-tap on the momentary footswitch (one tap remains for bypassing the effect). A second function of the microcontroller could be to switch from normal bypass to trails-bypass (with a long press on the momentary footswitch). A dual colour LED could be used to show in which of the delay or echo mode we are. And the microcontroller could be programmed to blink the LED as the bypass mode is changed (normal <-> trails).

But I think I'll need to perform all these mods in a new larger enclosure!
Cornish made his Tape Echo Simulator (TES) from a boss DD2. I think I'll make soon my Loylo TES from a DE7. :lol: :oops:
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Re: Ibanez DE-7 mods thread

Postby flowmastergfunk » 17 Oct 2014, 20:35

Awesome! I have been looking a lot lately into what it would take to solve the trails mystery, and didn't realize that this thread had a significant update! Looking forward to getting back into my shop so I can check this out on an actual computer and put it to the test! Big props on all the hard work and research! I would like to set mine up for permanent trails. I use several other delays on my board without trails, so it will be great to have perma-trails for this unit! Can always do true bypass around it, should I decide to change my mind :) oh wait...I have an extra de7 on hand at all times, should I decide to change my mind lol
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Re: Ibanez DE-7 mods thread

Postby Tube2stomp » 04 Mar 2016, 16:14

Thanks a lot for the detailed mods!!!

Where did you cut the signal to insert a repeats external loop (send/return)? is it simply a wire in/out to the stereo jack or did you add some resistance/caps or something?
Do you have any tip on how and where is best to make a lows/bass rolloff mod? this is a major characteristic of tape delays.

Those mini sliders you used are sweet :lol:
The pedal looks like it should have been like that from the get go.
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Re: Ibanez DE-7 mods thread

Postby kuato » 28 Oct 2019, 01:32

I hope you don't mind me resurrecting this thread..

While searching for a DE7 I came across this guy who owns several copies of the pedal and one of the Chinese pedals self-oscillates in 'Delay' mode. He recorded a video to show it in action: https://www.youtube.com/watch?v=DrQza7kbYgw

I've tried 4-5 copies of this pedal and they're all slightly different so I realize there's quite a bit of variation of the components/tolerances. Would it would be possible to mod the pedal to enable infinite repeats using the 'Delay' setting?

I'd really appreciate any help with this.
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Re: Ibanez DE-7 mods thread

Postby Motter » 04 Feb 2020, 18:11

Could modulation be added to the repeats with an LFO and optocoupler in parallel with the Delay Time pot?
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Re: Ibanez DE-7 mods thread

Postby chance_smith » Yesterday, 05:29

I’d really like to add a blinking light to match the repeats (on and bypassed).

I’d also like to add a relay for true bypass. So I need to figure out how to keep the effect always on. Also, if I add a relay pcb to switch this thing on and off, I’m pretty sure trails is just a matter of changing the value of a resistor in the relay circuit.

Any thoughts?
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